ABSTRACT
The main protease (Mpro) is one of the best-characterized drug targets among coronaviruses. In the current study, we adopted a multiple cross-docking strategy against different crystal structures of SARS-CoV-2 Mpro to perform computer-based high-throughput virtual screening of possible inhibitors from a drug database using Autodock Vina and SeeSAR software, combined with our in-house automatic processing scripts. The KDs between screened candidates and Mpro were determined using Biacore. Seven drugs were found to fit the substrate-binding pocket of Mpro with a stable conformation, showing high KDs that ranged from 6.79E-7 M to 5.20E-5 M. Finally, mutagenesis studies confirmed that these drugs interact with Mpro specifically, suggesting that our method was reliable and convincing. Given the safety of these old drugs, they may serve as promising candidates to treat the infection of SARS-CoV-2. Our results also provide rational explanations for the behaviour of five drugs evaluated in clinical trials.